It is known from, for example U.S. Pat. No. 6,557,518, to provide an oil restriction in oil control passages used to supply oil to deactivatable hydraulic lash adjusters in order to purge the control passages of gaseous vapor so that proper operation of the deactivation mechanisms is available when needed.
It is a problem with such an arrangement that the small size of the oil restriction can lead to blockage of the passage if any debris enters the restriction. It is a further problem associated with the prior art that such a restriction is difficult to clear if such a blockage does occur. Said problems have been recognized by the inventors herein.
It is further known from, for example U.S. Pat. No. 6,484,680, to provide a restrictor and filter assembly for use with a variable cam timing unit of an engine. The restrictor and filter assembly is press fitted into one of the oil passages in the engine and so is not easy to remove should the filter(s) become blocked. In addition, the restrictor and filter assembly only filters the oil entering the restrictor from one side and so is not suitable for use in situations where there is bidirectional flow through the restrictor.
One example approach to address these issues recognized by the inventors may include a combined oil filter and restrictor assembly that is easy to fit or remove and which provides filtration of the oil flowing through an oil restrictor irrespective of the direction of the oil flow.
According to a first aspect of the present application there is provided a combined oil filter and restrictor assembly comprising a filter and restrictor unit and a metal threaded member for sealingly retaining the filter and restrictor unit in position, wherein the filter and restrictor unit comprises a tubular body having a cylindrical side wall defining at least one primary oil access port located in the cylindrical side wall at a position spaced away from a first end of the tubular body, an oil flow restrictor located in the primary bore, a first filter located between a first end of the oil flow restrictor and the at least one primary oil access port and a second filter located between a second oil access port and a second end of the flow restrictor such that the oil flow restrictor is interposed between the first and second oil filters.
The oil flow restrictor may comprise a restrictor body defining a small diameter bore and the restrictor body is located in a primary bore defined by the cylindrical wall of the tubular body.
The second oil filter may be secured in position by the restrictor body.
An end portion of the tubular body may be engaged with a bore in an end portion of the threaded member so as to attach the tubular body to the threaded member.
The tubular body may be made from a plastics material.
The threaded member may have a head portion and a threaded body portion separated from the head portion by a circumferential groove for accommodating, in use, a resilient seal.
The head portion and a bore in a component with which the threaded member is threadingly engaged in use.
The head portion may have a drive means for use in securing the combined oil filter and restrictor assembly in position.
The first oil filter may comprise a cylindrical filter element positioned within the tubular body so as to overly the at least one primary oil access port.
According to a second aspect of the present application there is provided an assembly comprising a structural metal component and a combined oil filter and restrictor assembly constructed in accordance with said first aspect of the present application, the structural metal component defining at least two oil passages and a threaded cross bore joining a first oil passage of the at least two oil passages to a second one of the at least two oil passages, the metal threaded member of the combined oil filter and restrictor assembly is threadingly engaged with the threaded cross bore, the first oil passage is arranged to be in fluid communication with the at least one primary oil access port of the combined oil filter and restrictor assembly and the at least one second oil passage is arranged to be in fluid communication with the second oil access port of the combined oil filter and restrictor assembly.
The threaded cross bore may include a tapered portion for cooperation with the frusto-conical surface on the head portion of the threaded member so as to form a seal therebetween.
The tubular body may have at least one external circumferential rib thereon for sealing engagement with the threaded cross bore in the metal component.
The structural metal component may be a cylinder head of an engine.
According to a third aspect of the present application there is provided a variable displacement engine having at least one deactivatable cylinder, a cylinder head forming the structural metal component of an assembly constructed in accordance with said second aspect of the present application and at least one deactivatable hydraulic lash adjuster associated with a valve supported by the cylinder head wherein, when all of the cylinders of the engine are active, the combined oil filter and restrictor assembly permits a restricted purge flow of oil to flow from an oil supply passage for the at least one deactivatable hydraulic lash adjuster to a signal oil passage for the at least one deactivatable hydraulic lash adjuster so as to purge the signal oil passage.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.